Monomeric silicon chemicals are known as silanes. A silane structure and an analogous carbon-based structure are shown as follows:

The four substituents above demonstrate differences and similarities in physical and chemical properties between silicon- and carbon-based chemicals. A silane that contains at least one carbon-silicon bond (CH3—Si—) structure is known as an organosilane. The carbon-silicon bond is very stable, very non-polar and gives rise to low surface energy, non-polar, hydrophobic effects. Similar effects can be obtained from carbon-based compounds, although these effects are often enhanced with silanes. The silicon hydride (—Si—H) structure is very reactive. It reacts with water to yield reactive silanol (—Si—OH) species and, additionally, will add across carbon-carbon double bonds to form new carbon-silicon-based materials. The methoxy group on the carbon compound gives a stable methyl ether, while its attachment to silicon gives a very reactive and hydrolyzable methoxysilyl structure. The organofunctional group, the aminopropyl substituent, will act chemically the same in the organosilicon compound as it does in the carbon-based compound. The distance of the amine, or other organofunctional group, from silicon will determine whether the silicon atom affects the chemistry of the organofunctional group. If the organic spacer group is a propylene linkage (e.g., —CH2CH2CH2—), then the organic reactivity in the organo-functional silane will be similar to organic analogs in carbon chemistry.
Certain reactive silanes, particularly vinyl silanes (—Si—CH═CH2) and silicon hydrides (—Si—H), are useful reactive groups in silicon chemistry, even though the reactive group is attached directly to the silicon atom. Attachment of chlorine, nitrogen, methoxy, ethoxy or acetoxy directly to silicon yields chlorosilanes, silyl-amines (silazanes), alkoxysilanes and acyloxysilanes, respectively, are very reactive and exhibit unique inorganic reactivity. Such molecules will react readily with water, even moisture adsorbed on a surface, to form silanols. These silanols then can react with other silanols to form a siloxane bond (—Si—O—Si—), a very stable structure; or in the presence of metal hydroxyl groups on the surface of glass, minerals or metals, silanols will form very stable —Si—O-metal bonds to the surface. This is the key chemistry that allows silanes to function as valuable surface-treating and coupling agents. Chloro-, alkoxy-, and acetoxy-silanes and silazanes (—Si—NH—Si) will react readily with an active hydrogen on any organic chemical (e.g., alcohol, carboxylic acid, amine, phenol or thiol) via a process called silylation:R3Si—Cl+R′OH→R3Si—OR′+HCl
Silylation is very useful in organic synthesis to protect functional groups while other chemical manipulations are being performed. The silylated organofunctional group can be converted back to the original functional group once the chemical operation is completed. Silylation is very important in the manufacture of pharmaceutical products.
Silane coupling agents are silicon-based chemicals that contain two types of reactivity—inorganic and organic—in the same molecule. A typical general structure is:
where RO is a hydrolyzable group, such as methoxy, ethoxy, or acetoxy, and X is an organofunctional group, such as amino, methacryloxy, epoxy, etc.
A silane coupling agent will act as an interface between an inorganic substrate (such as glass, metal or mineral) and an organic material (such as an organic polymer, coating or adhesive) to bond, or couple, the two dissimilar materials.
RnSi(OR)4-n is the basic structure of organosilanes with “R” being an alkyl, aryl, or an organofunctional group and “OR” being a methoxy, ethoxy, or acetoxy group. Some examples of organosilanes include amino silanes, epoxysilanes, methacrylsilanes, phenylsilanes, alkylsilanes, chlorosilanes, vinylsilanes, sulfur substituted silanes etc.
The prevalent use and manufacture of organosilanes produces various process streams that contain organsilanes. In addition, depolymerization processes that are used to recover monomers from silicone containing materials, including silicone wastes, produce organosilane containing solutions.
The present invention is directed to a method for removing organosilanes from various sources, including process streams, waste streams, recycling streams and solutions.